Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     env:
       DEVELOPER_DIR: /Applications/Xcode_16.1.app/Contents/Developer
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
       with:
         submodules: recursive
     - name: Build

.github/workflows/codeql.yml

@@ -28,7 +28,7 @@ jobs:
           build-mode: autobuild
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.github/workflows/lint.yml

@@ -13,15 +13,15 @@ jobs:
   SwiftLint:
     runs-on: macos-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: irgaly/setup-mint@v1
     - name: SwiftLint
       run: mint run swiftlint --strict
   SwiftFormat:
     runs-on: macos-latest
     needs: SwiftLint
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: irgaly/setup-mint@v1
     - name: SwiftFormat Lint
       run: mint run swiftformat --lint .
@@ -30,6 +30,6 @@ jobs:
     env:
       DEVELOPER_DIR: /Applications/Xcode_16.1.app/Contents/Developer
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Swift-Docc Validate
       run: swift package generate-documentation --analyze --warnings-as-errors